alpha: switch osf_mount() to strndup_user()

... same as native mount(2) is doing for devname argument.  While we
are at it, fix misspelling ufs_args as cdfs_args in osf_ufs_mount() -
layouts are identical, so it doesn't change anything, but the current
variant is confusing for no reason.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

arch/alpha/kernel/osf_sys.c

@@ -454,42 +454,30 @@ static int
 osf_ufs_mount(const char __user *dirname,
 	      struct ufs_args __user *args, int flags)
 {
-	int retval;
-	struct cdfs_args tmp;
-	struct filename *devname;
+	struct ufs_args tmp;
+	char *devname __free(kfree) = NULL;
 
-	retval = -EFAULT;
 	if (copy_from_user(&tmp, args, sizeof(tmp)))
-		goto out;
-	devname = getname(tmp.devname);
-	retval = PTR_ERR(devname);
+		return -EFAULT;
+	devname = strndup_user(tmp.devname, PATH_MAX);
 	if (IS_ERR(devname))
-		goto out;
-	retval = do_mount(devname->name, dirname, "ext2", flags, NULL);
-	putname(devname);
- out:
-	return retval;
+		return PTR_ERR(devname);
+	return do_mount(devname, dirname, "ext2", flags, NULL);
 }
 
 static int
 osf_cdfs_mount(const char __user *dirname,
 	       struct cdfs_args __user *args, int flags)
 {
-	int retval;
 	struct cdfs_args tmp;
-	struct filename *devname;
+	char *devname __free(kfree) = NULL;
 
-	retval = -EFAULT;
 	if (copy_from_user(&tmp, args, sizeof(tmp)))
-		goto out;
-	devname = getname(tmp.devname);
-	retval = PTR_ERR(devname);
+		return -EFAULT;
+	devname = strndup_user(tmp.devname, PATH_MAX);
 	if (IS_ERR(devname))
-		goto out;
-	retval = do_mount(devname->name, dirname, "iso9660", flags, NULL);
-	putname(devname);
- out:
-	return retval;
+		return PTR_ERR(devname);
+	return do_mount(devname, dirname, "iso9660", flags, NULL);
 }
 
 static int